Acetabular reamer

ABSTRACT

An acetabular reaming system is disclosed of the type having a driver and a tool held together by a quick-release coupling mechanism The tool ( 10 ) has a hollow body ( 12 ) defining a domed shape with a rotational axis ( 14 ), an apex ( 16 ) aligned with the axis ( 14 ) and a hemispherical wall ( 18 ) extending from the apex ( 16 ) to an equatorial rim ( 20 ) spaced 90 degrees from the axis ( 14 ). The rim ( 20 ) has an edge ( 22 ) visible to the user that indicates the position of the tool ( 10 ) relative to the bone. A first plurality of cutting sites ( 24 ) is arrayed along the body ( 12 ) and a second plurality of cutting sites ( 28 ) is arrayed circumferentially along the edge ( 22 ). Preferably, the first plurality of cutting sites ( 24 ) present raised first teeth ( 30, 130, 230, 330 ) having a profile selected from continuous squared ( 30 ), continuous rounded ( 130 ), discontinuous squared ( 230 ) and tongued ( 330 ) profiles. Also preferably, the second plurality of cutting sites ( 28 ) present raised second teeth ( 32, 132, 232, 332, 432 ) selected from continuous squared ( 32 ), continuous rounded ( 132 ), discontinuous squared ( 232 ), tongued ( 332 ) and bladed ( 432 ) profiles.

TECHNICAL FIELD

[0001] The present invention relates to surgical cutting tools and instrumentation systems that utilize such tools, particularly tools having a domed shape for reaming a hemispherical bone cavity.

BACKGROUND

[0002] Acetabular reaming systems are well known in hip arthroplasty, to prepare bone tissue for receiving a hemispherical implant U.S. Pat. No. 5,658,290 to one of the present inventors, the entire contents of which are expressly incorporated by reference herein and relied-upon, discloses such a system. In the afore-mentioned patent, a surgical driver includes a quick disconnect mechanism having catches that receive a pair of orthogonal bars from a domed cutting tool.

[0003] It is highly desirable that the bone is shaped by the rotary tool into a cavity that conforms closely in hemispherical shape and dimension to the implant being received. Those skilled in the art have sought to provide rotary cutting tools that form the bone into a precise hemispherical cavity. It is further desirable to advance the tool linearly into the bone to fully cut the cavity, versus having to rock the tool sideways by changing its orientation to achieve a complete shape.

[0004] For example, one system has a tool with a cylindrical rim that continues parallel past the hemispherical equator of the tool, in order to allow presentation of teeth for a full cut. Such prior domed tools are referred to as “high-rim” reamers. Although these high-rim reamers have teeth presented for a straight-in (linear) advancement of cut into the cavity, there is no visual confirmation guiding the user to the finished cut. Actual position of the outer equatorial edge of the tool in the bone cavity is obscured and the user does not know exactly when to stop pushing in the tool.

[0005] Another type of tool is found in what is known as “hemispherical” reaming systems. These tools have no teeth presented for a full cut of the cavity simply by linear advancement of the tool into the bone. That is, a full, a straight-in cut is not possible hence the tool must be rocked sideways in order to present the teeth for cutting the final shape. This may result in over-cutting of the cavity.

[0006] Accordingly, a need exists for an improved reaming system wherein the user may precisely ascertain the swath being cut by the tool as it bottoms-out in the bone, to completely form the hemispherical-shaped cavity without the risk of over-cutting. Particularly, there is a need for visual confirmation by the user of the position of the equatorial edge of the tool as the cavity is being fully cut.

[0007] There is also a need for an improved reaming system wherein the tool is linearly advanced without having to “rock” the tool by changing the orientation of the cutting approach, in order to achieve a full cut.

[0008] There is a further need for a rotary cutting tool having a tooth design that precisely cuts a cavity with the desired size and shape of an implant to be received in the cavity, while employing a linear cut guided by accurate visual confirmation by the user.

SUMMARY OF INVENTION AND ADVANTAGES

[0009] According to an embodiment of the present invention, there is provided a tool for cutting a hemispherical cavity in bone. The tool is preferably part of a reaming system that utilizes a driver with quick disconnect catches that receive mounting bars on the tool. The tool has a hollow body defining a domed shape with a rotational axis, an apex aligned with the axis and a hemispherical wall extending from the apex to an equatorial rim spaced 90 degrees from the axis. The rim has an edge visible to the user that indicates the position of the tool relative to the bone. A first plurality of cutting sites is arrayed along the body and at least one equatorial cutting site is located along the edge. Preferably the first cutting sites are open and the equatorial site closed.

[0010] In a preferred embodiment, the first plurality of cutting sites present raised first teeth having a profile selected from squared, rounded and tongued profiles.

[0011] In another preferred embodiment, the equatorial cutting site of the tool presents a raised second tooth selected from squared, rounded, tongued and bladed profiles.

[0012] According to another embodiment of the invention, the tool has a hollow body defining a domed shape with a rotational axis, an apex aligned with the axis and a hemispherical wall extending from the apex to an equatorial rim spaced 90 degrees from the axis. The rim has an edge visible to the user that indicates the position of the tool relative to the bone. A first plurality of cutting sites is arrayed along the body and a second plurality of cutting sites is arrayed circumferentially along the edge. Preferably, the first plurality of cutting sites present raised first teeth having a profile selected from squared, rounded and tongued profiles. Also preferably, the second plurality of cutting sites present raised second teeth selected from squared, rounded, tongued and bladed profiles.

[0013] According to yet another embodiment of the invention, the tool has a hollow body defining a domed shape with a rotational axis, an apex aligned with the axis and a hemispherical wall extending from the apex to an equatorial rim spaced 90 degrees from the axis. The rim has an edge visible to the user that indicates the position of the tool relative to the bone. A first plurality of cutting sites is arrayed along the body and a second plurality of cutting sites is arrayed circumferentially along the edge on downwardly depending lobes, which lobes preferably continue with substantially the same radius of curvature past the equator of the tool. Preferably, the first plurality of cutting sites present raised first teeth having a profile selected from squared, rounded and tongued profiles. Also preferably, the second plurality of cutting sites present raised second teeth selected from squared, rounded and tongued profiles.

[0014] In still another embodiment of the invention, the tool has a hollow body defining a domed shape with a rotational axis, an apex aligned with the axis and a hemispherical wall extending from the apex to an equatorial rim spaced 90 degrees from the axis. The rim has an edge visible to the user that indicates the position of the tool relative to the bone. At least one mounting bar, and preferably a pair of, mounting bars, extends across the underside of the body between diametrically opposed locations on the rim. A first plurality of cutting sites is arrayed along the body and a second plurality of cutting sites is outboard of the diametrically opposed locations at the edge. Preferably, the second plurality of cutting sites is closed. It is also preferred that the second plurality of cutting sites present bladed teeth essentially extending outboard from the bars.

[0015] An advantage of the present invention is the capability to perform an essentially perfect hemispherical cut, where the depth can be assessed clearly during the cut.

[0016] Another advantage of the invention is a tool presenting cutting sites that allow a full cut with clear visual confirmation while the user linearly advances the tool into the bone, without needing to change the orientation of the surgical driver and hence ‘rock’ the tool.

[0017] A further advantage of the invention is that, in preferred embodiments, the equatorial teeth are contained at closed cutting sites, which avoids risk of tissue entrapment.

[0018] Other objects and advantages will become apparent to a reader skilled in the art, with reference to the following Figures and accompanying Detailed Description wherein textual reference characters correspond to those denoted on the Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is an elevational view of a tool of the present invention, showing an equatorial tooth with a preferred flattened profile;

[0020]FIG. 1A is a schematic view of the tooth configuration shown in FIG. 1;

[0021]FIG. 2 is an elevational view of the tool of the of FIG. 1, showing an equatorial tooth with a preferred rounded profile;

[0022]FIG. 2A is a schematic view of the tooth configuration shown in FIG. 2;

[0023]FIG. 3 is a perspective view of FIG. 1, showing an equatorial tooth with a preferred tongued profile;

[0024]FIG. 3A is a schematic view of the tooth configuration shown in FIG. 3,

[0025]FIG. 4 is a perspective view of a preferred tool of the invention, showing a closed equatorial cutting site containing a flattened tooth profile;

[0026]FIG. 5 is a perspective view of a preferred tool of the invention, showing closed equatorial cutting sites containing bladed teeth representing outboard extensions of the mounting bars;

[0027]FIG. 6 is an elevational view of a cutting tool of the present invention, showing equatorial cutting sites located on downwardly depending lobes, which contain rounded teeth;

[0028]FIG. 6A is a schematic view of a representative equatorial cutting site on a preferred downwardly depending lobe at the edge of the rim of the body shown in FIG. 6;

[0029]FIG. 7 is a perspective view of FIG. 6;

[0030]FIG. 7A, is a schematic view of the equatorial tooth configuration shown in FIG. 7; and

[0031]FIG. 8 is a perspective view of the reaming system of the invention, showing a tool and driver connected together and ready for use.

DETAILED DESCRIPTION

[0032] According to the present invention, there is provided a reaming system for cutting a hemispherical cavity in bone. Referring to FIGS. 1-7, the system has a tool 10 that utilizes a driver 11, shown in FIG. 8 with quick disconnect mechanism that receives the tool 10 for use. The structure and operation of driver 11 and its connecting mechanism is amply described in the aforementioned U.S. Pat. No 5,658,290, which is essentially the same as the driver-tool mechanism shown by FIG. 8. Of course, other connecting mechanisms could be employed, such as a central boss provided on the tool, as described in WO 99/47051 of one of the present inventors. As shown by WO 99/47051, a single mounting bar could be used with one pair diametrically opposed ends, versus the pair of intersecting mounting bars shown in the '290 patent mentioned immediately above.

[0033] Referring to FIGS. 1-3, the tool 10 has a hollow body 12 defining a domed shape with a rotational axis 14, an apex 16 aligned with the axis 14 and a hemispherical wall 18 extending from the apex 16 to an equatorial rim 20 spaced 90 degrees from the axis 14. The rim 20 has an edge 22 visible to the user that indicates the position of the tool 10 relative to the bone. A first plurality of cutting sites 24 is arrayed along the body 12 and at least one equatorial cutting site 28 is located along the edge 22.

[0034] Referring to FIGS. 1-7, the first plurality of cutting sites 24 present raised first teeth 30, 130, 230 preferably having a profile selected from squared 30 (FIGS. 4-5), rounded 130 (FIGS. 7-8) and tongued 232 profiles. A suitable tongued profile tooth 232 is taught in U.S. Pat. No. 5,968,049, the entire disclosure of which is incorporated by reference herein and relied upon. The tongued tooth 232 may either be serrated, as shown in the '049 patent, or non-serrated. Similarly, where the equatorial tooth 232 has a tongued profile (FIG. 3), it is as shown in the '049 patent.

[0035] In FIG. 1A, the tooth 32 is formed or results from bending the tooth 32 outward, leaving a flattened tooth with no side relief and rounded edges. In FIG. 2, the rounded tooth 132 is commonly known as a “cheese grater” tooth, manufactured with a high ram that is then later removed (FIG. 2A) to reveal a hemisphere with a cheese grater tooth-style at the edge

[0036] Referring to FIGS. 1-3 and 5-7, the equatorial cutting site 28 presents a raised second tooth 32, 132, 232, 332 selected from squared 32 (FIG. 1), rounded 132 (FIGS. 2, 6-7), tongued 232 (FIG. 3) and bladed 332 (FIG. 5) profiles.

[0037] Referring to FIGS. 1-7, the tool 10 has a hollow body 12 defining a domed shape with a rotational axis 14, an apex 16 aligned with the axis 14 and a hemispherical wall 18 extending from the apex 16 to an equatorial rim 20 spaced 90 degrees from the axis 14. The rim 20 has an edge 22 visible to the user that indicates the position of the tool 10 relative to the bone. A first plurality of cutting sites 24 is arrayed along the body 12 and a second plurality of cutting sites 28 is arrayed circumferentially along the edge 22. Preferably, the first plurality of cutting sites 24 present raised first teeth 30, 130, 230, 330 having a profile selected from squared 30, rounded 130, squared 230 and tongued 330 profiles. Also preferably, the second plurality of cutting sites 28 present raised second teeth 32, 132, 232, 332 selected from squared 32, rounded 132, tongued 232 and bladed 332 profiles. In FIGS. 1-3, body 12 is formed by starting with a hollow domed shape, with the wall 18 extending beyond the 90-degree equator (shown in phantom) and then cut. The equatorial teeth 32, 132, 232 are formed and wall 18 is then cut at the 90-degree equator so that the teeth are open on their lower side.

[0038] Referring to FIGS. 6-7, the tool 10 has a hollow body 12 defining a domed shape with a rotational axis 14, an apex 16 aligned with the axis 14 and a hemispherical wall 18 extending from the apex 16 to an equatorial rim 20 spaced 90 degrees from the axis 14. The rim 70 has an edge 22 visible to the user that indicates the position of the tool 10 relative to the bone. A first plurality of cutting sites 24 is arrayed along the body 12 and a second plurality of cutting sites 28 is arrayed circumferentially along the edge 22 on downwardly depending lobes 36. The wall 18 continues past the equator of the tool 10 with the same radius of curvature as the rest of wall 18, rather than being made cylindrical at the equator. This continued curvature assures that the correct shape is being cut, even if the tool 10 is not advanced entirely in a linear fashion into the bone cavity being cut. Preferably, the first plurality of cutting sites 24 present raised first teeth 30, 130, 230, 330 having a profile selected from squared 30, rounded 130, squared 230 and tongued 330 profiles. Also preferably, the second plurality of cutting sites 28 present raised second teeth 32, 132 selected from squared 32 or rounded 132 profiles. The lobes 36 curve downwardly and inwardly, having the same curvature as the upper part of the wall 18 rather than being cylindrical in shape.

[0039] Referring to FIGS. 4-5, the body 12 has at least one mounting bar 34 tending between the axis 14 and rim 20, with a tooth 32, 332 which, in FIG. 5 is an essentially contiguous radial projection or blade formed from the bar 34 outboard of the rim 20 along edge 22. The first plurality of cutting sites 24 preferably contains openings 25 for passage of debris, whereas the second plurality of sites 28 may be either open (FIGS. 1-2 and 6-7) or closed (FIGS. 4-5).

[0040] Preferably, the second plurality of teeth 32, 132, 232 are discontinuous, i.e., relieved on one side, with respect to the tool 10 shown in FIGS. 1-3. Teeth 32, 132, 232 are made discontinuous by cutting away the material of the body 12, shown in phantom (FIGS. 1-3) once the teeth are formed. Machining of the teeth 32, 132, 232 in body 12 is depicted in FIGS. 1A, 2A and 3A, respectively. By contrast, in FIGS. 6-7 the teeth 132 are continuous.

[0041] While one or more preferred embodiments of the present invention have been described, it should be understood that various changes, adaptations and modifications might be made without departing from the spirit of the invention and the scope of the appended claims. 

1. A tool (10) for cutting a hemispherical cavity in bone, comprising. a) a hollow body (12) defining a domed shape with a rotational axis (14), an apex (16) aligned with the axis (14) and a hemispherical wall (18) extending from the apex (16) to an equatorial rim (20) spaced 90 degrees from the axis (14), the rim (20) having an edge (22) visible to the user that indicates the position of the tool (10) relative to the bone; b) a first plurality of cutting sites (24) arrayed along the body (12); and c) at least one cutting site (28) along the edge (22).
 2. The tool (10) of claim 1 wherein the first plurality of cutting sites (24) present raised first teeth (30, 130) having a profile selected from a group consisting of squared (30), rounded (130) and tongued profiles.
 3. The tool (10) of claim 1 wherein the cutting site of c) presents a raised second tooth (32, 132, 232, 332) selected from a group consisting of squared (32), rounded (132), tongued (232) and bladed (332) profiles.
 4. The tool (10) of claim 2 wherein the cutting site (28) of c) presents a raised tooth (32) having a squared profile.
 5. The tool (10) of claim 2 wherein the cutting site (28) of c) presents a raised tooth (132) having a rounded profile.
 6. The tool (10) of claim 2 wherein the cutting site (28) of c) is closed.
 7. The tool (10) of claim 2 wherein the cutting site (28) of c) presents a raised tooth (232) having a tongued profile.
 8. The tool (10) of claim 2 wherein the cutting site (28) of c) presents a raised tooth (332) having a bladed profile.
 9. The tool (10) of claim 3 wherein the first plurality of cutting sites (24) presents raised first teeth (28) having a squared profile.
 10. The tool (10) of claim 3 wherein the first plurality of cutting sites (24) presents raised first teeth (28) having a rounded profile.
 11. The tool (10) of claim 3 wherein the equatorial cutting site (28) is closed.
 12. The tool (10) of claim 3 wherein the first plurality of cutting sites (24) presents raised first teeth having a tongued profile.
 13. The tool (10) of claim 3 wherein the body (12) has at least one mounting bar (34) extending between the axis (14) and rim (20).
 14. The tool (10) of claim 13 wherein the raised tooth of c) has a bladed profile.
 15. The tool (10) of claim 14 wherein the bladed tooth is an essentially contiguous radial projection of the bar (34) outboard of the rim (20).
 16. The cutting tool (10) of claim 15 wherein the cutting site (28) of c) is closed.
 17. A tool (10) for cutting a hemispherical cavity in bone, comprsing: a) a hollow body (12) defining a domed shape with a rotational axis (14), an apex (16) aligned with the axis (14) and a hemispherical wall (18) extending from the apex (16) to an equatorial rim (20) spaced 90 degrees from the axis (14), the rim (20) having an edge (22) visible to the user that indicates the position of the tool (10) relative to the bone; b) a first plurality of cutting sites (24) arrayed along the body (12) and presenting raised first teeth (30, 130); and c) a second plurality of cutting sites (28), circumferentially arrayed along the edge (22) and presenting raised second teeth (32, 132, 232, 332).
 18. The tool (10) of claim 17 wherein the first plurality of cutting sites (24) present raised first teeth (30, 130) having a profile selected from a group consisting of squared (30), rounded (130) and tongued profiles.
 19. The tool (10) of claim 17 wherein the second plurality of cutting sites presents raised second teeth (32, 132, 232, 332) selected from a group consisting of squared (32), rounded (132), tongued and bladed (332) profiles.
 20. The tool (10) of claim 18 wherein the second plurality of cutting sites presents raised second teeth (32) having a squared profile.
 21. The tool (10) of claim 18 wherein the second plurality of cutting sites presents raised second teeth (132) having a rounded profile.
 22. The tool (10) of claim 18 wherein the second plurality of cutting sites presents raised second teeth (232) having a tongued profile.
 23. The tool (10) of claim 18 wherein the second plurality of cutting sites presents raised second teeth (332) having a bladed profile.
 24. The tool (10) of claim 19 wherein the first plurality of cutting sites (24) presents raised first teeth (28) having a squared profile.
 25. The tool (10) of claim 19 wherein the fist plurality of cutting sites (24) presents raised first teeth (130) having a rounded profile.
 26. The tool (10) of claim 19 wherein the fist plurality of cutting sites (24) presents raised first teeth (30) having a squared profile.
 27. The tool (10) of claim 19 wherein the first plurality of cutting sites (24) presents raised first teeth (232) having a tongued profile.
 28. The tool (10) of claim 23 wherein the body has at least one mounting bar extending between the axis and rim, the bladed teeth (332) further comprising essentially contiguous radial projections of the bars (34) outboard of the edge (22).
 29. The tool (10) of claim 18 wherein the first plurality of cutting sites (24) have openings for passage of debris.
 30. The cutting tool (10) of claim 19 wherein the second plurality of cutting sites are closed.
 31. A tool (10) for cutting a hemispherical cavity in bone, comprising: a) a hollow body (12) defining a domed shape with a rotational axis (14), an apex (16) aligned with the axis (14) and a hemispherical wall (18) extending from the apex (16) to a discontinuous equatorial rim (20) spaced 90 degrees from the axis (14), the rim (20) having an edge (22) with downwardly depending lobes (36) visible to the user that indicates the position of the tool (10) relative to the bone; b) a first plurality of cutting sites (24) arrayed along the body (12) and presenting raised first teeth (30, 130); and c) a second plurality of cutting sites (28), located on the downwardly depending lobes (36) and presenting raised second teeth (132).
 32. The tool (10) of claim 31 wherein the first plurality of cutting sites (24) present raised first teeth (30, 130) having a profile selected from a group consisting of squared (30), rounded (130) and tongued profiles.
 33. The tool (10) of claim 31 wherein the second plurality of cutting sites presents raised second teeth ( 32) having a rounded (132) profile.
 34. The tool (10) of claim 32 wherein the second plurality of cutting sites presents raised second teeth (132) having a continuous rounded profile.
 35. The tool (10) of claim 33 wherein the first plurality of cutting sites (24) have openings for passage of debris.
 36. The cutting tool (10) of claim 33 wherein the second plurality of cutting sites are closed.
 37. The cutting tool of claim 31 wherein the downwardly depending lobes (36) have a curvature substantially similar to that of the wall (18).
 38. A surgical reaming system comprising; a) a driver connected to a source of rotary power and having catches; and b) a tool having i) a hollow body (12) defining a domed shape with a rotational axis (14), an apex (16) aligned with the axis (14) and a hemispherical wall (18) extending from the apex (16) to a discontinuous equatorial rim (20) spaced 90 degrees from the axis (14), the rim (20) having au edge (22) with downwardly depending lobes (36) visible to the user that indicates the position of the tool (10) relative to the bone, ii) a first plurality of cutting sites (24) arrayed along the body (12) and presenting raised first teeth (30, 130) and iii) a second plurality of cutting sites (28), located on the edge and presenting raised second teeth (32, 1320, 232, 332).
 39. The reaming system of claim 38 wherein the second teeth (32, 132, 232, 332) are discontinuous. 